Intercept-temperature drift calibration of a signal strength detector
A device may include an intercept-temperature drift input to receive an intercept-temperature drift value. The device may further include a reference current generator that generates a reference current based at least in part on the intercept-temperature drift value. Additionally, the device may include an analog signal chain that adjusts a slope-temperature drift of the signal-strength detector by adjusting a delta proportional to absolute temperature of the analog signal chain.
1 . A signal-strength detector comprising:
an intercept-temperature drift input to receive an intercept-temperature drift value;
a reference current generator that generates a reference current based at least in part on the intercept-temperature drift value, wherein the reference current generator generates the reference current as a weighted sum of a proportional to absolute temperature (PTAT) current and a complementary to absolute temperature (CTAT) current; and
an analog signal chain that adjusts an intercept-temperature drift of the signal-strength detector based at least in part on the reference current.
2 . The signal-strength detector of claim 1 , wherein the reference current includes a trim value determined based at least in part on the intercept-temperature drift value, wherein inclusion of the trim value with the reference current causes adjustment of the intercept-temperature drift of the signal-strength detector.
3 . The signal-strength detector of claim 1 , wherein adjusting a ratio of the PTAT current to the CTAT current adjusts the intercept-temperature drift of the signal-strength detector.
4 . The signal-strength detector of claim 1 , wherein the analog signal chain includes the reference current generator.
5 . The signal-strength detector of claim 1 , wherein the reference current generator comprises a first current digital to analog converter (IDAC) configured to weight the PTAT current and a second IDAC configured to weight the CTAT current.
6 . The signal-strength detector of claim 5 , wherein a sum of the weighted PTAT current and the weighted CTAT current provides a fine adjustment of the reference current, and wherein the reference current generator further comprises a third IDAC that provides a coarse adjustment of the reference current.
7 . The signal-strength detector of claim 1 , further comprising a resistive heater configured to apply heat to the analog signal chain.
8 . The signal-strength detector of claim 7 , wherein the resistive heater is configured to support an OFF state and a plurality of ON states, wherein each ON state of the plurality of ON states causes a different amount of heat to be applied to the analog signal chain.
9 . The signal-strength detector of claim 7 , wherein the intercept-temperature drift value is determined based at least in part on a plurality of output values of the signal-strength detector obtained for an input current at a plurality of temperature values and a plurality of reference current values.
10 . The signal-strength detector of claim 9 , wherein the resistive heater applies different amounts of heat to the analog signal chain to obtain the plurality of temperature values.
11 . The signal-strength detector of claim 9 , wherein the intercept-temperature drift value is determined using regression analysis on the plurality of output values of the signal-strength detector obtained for the input current at the plurality of temperature values and the plurality of reference current values.
12 . The signal-strength detector of claim 1 , further comprising a non-volatile memory configured to store the intercept-temperature drift value, and wherein the reference current generator accesses the intercept-temperature drift value from the non-volatile memory.
13 . The signal-strength detector of claim 1 , further comprising an interface circuit configured to receive the intercept-temperature drift value from the intercept-temperature drift input and to store the intercept-temperature drift value at a non-volatile memory.
14 . The signal-strength detector of claim 1 , further comprising an analog temperature compensation circuit that adjusts a slope-temperature drift of the signal-strength detector by at least adding the PTAT current to a zero to absolute temperature (ZTAT) current.
15 . The signal-strength detector of claim 14 , wherein the analog temperature compensation circuit is connected in series with the analog signal chain, and wherein the analog temperature compensation circuit generates an output of the signal-strength detector corresponding to a measured signal strength of an input signal.
16 . The signal-strength detector of claim 14 , wherein the PTAT current is a trim current that is added to the ZTAT current and to a second PTAT current.
17 . The signal-strength detector of claim 14 , wherein the PTAT current is determined using regression analysis on a plurality of slope-temperature drift values at a plurality of temperatures applied by a resistive heater of the signal-strength detector.
18 . A photocurrent detection system comprising:
a photocurrent detector configured to receive a photocurrent output by a photodiode; and
a signal-strength detector configured to measure a signal strength of the photocurrent output, wherein the signal-strength detector comprises:
an intercept-temperature drift input to receive an intercept-temperature drift value;
a reference current generator that generates a reference current based at least in part on the intercept-temperature drift value; and
an analog signal chain that adjusts an intercept-temperature drift of the signal-strength detector based at least in part on the reference current.
19 . A method of calibrating a signal-strength detector, the method comprising:
causing a resistive heater of the signal-strength detector to be in an OFF state;
for an input current value corresponding to a photocurrent of a photodetector and when the resistive heater is in the OFF state,
sweeping a slope-temperature drift of an output value of the signal-strength detector generated based on the input current value among a range of slope-temperature drift values; and
for each slope-temperature drift value of the range of slope-temperature drift values, sweeping a reference current value among a range of reference current values to obtain a first set of intercept values;
causing the resistive heater to be in an ON state, wherein the resistive heater heats at least an analog signal chain of the signal-strength detector when in the ON state;
for the input current value corresponding to the photocurrent of the photodetector and when the resistive heater is in the ON state,
sweeping the slope-temperature drift of the output value of the signal-strength detector generated based on the input current value among the range of slope-temperature drift values; and
for each slope-temperature drift value of the range of slope-temperature drift values, sweeping the reference current value among the range of reference current values to obtain a second set of intercept values;
using the first set of intercept values and the second set of intercept values, performing linear regression to determine an intercept-temperature drift control value that minimizes intercept-temperature drift of the signal-strength detector; and
configuring a register value of the signal-strength detector with the intercept-temperature drift control value, wherein the signal-strength detector sets the reference current value based at least in part on the intercept-temperature drift control value during operation.